Abstract
Scanning Spreading Resistance Microscopy is a well-established technique for obtaining quantitative two- and three-dimensional carrier profiles in semiconductor devices with sub-nm spatial resolution. However, for sub-100 nm devices, the use of focused ion beam becomes inevitable for exposing the region of interest on a sample cross section. In this work, we investigate the impact of the focused ion beam milling on spreading resistance analysis and we show that the electrical effect of the focused ion beam extends far beyond the amorphous region and depends on the dopant concentration, ion beam energy, impact angle, and current density. For example, for dopant concentrations between 1.0 × 1020 and 1.5 × 1016 cm−3 we observe dopant deactivation at least between 23 and 175 nm for a glancing 30 keV ion beam. Further, we show that dopant deactivation is caused by defect diffusion during milling and is not directly impacted by the presence of Gallium in the sample. Later, we also discuss potential ways to mitigate these effects.
Highlights
Scanning Spreading Resistance Microscopy is a well-established technique for obtaining quantitative two- and three-dimensional carrier profiles in semiconductor devices with sub-nm spatial resolution
We have shown that the use of focused ion beam (FIB) for device cross-sectioning significantly impacts the subsequent electrical measurements on the surface using methods such as scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM) as the energetic Ga ions drastically change the crystallinity and electronic properties of the surface
Scalpel SSRM has been employed to reveal the extent of the electrical damage induced by the FIB irradiation along the Ga implantation depth
Summary
Scanning Spreading Resistance Microscopy is a well-established technique for obtaining quantitative two- and three-dimensional carrier profiles in semiconductor devices with sub-nm spatial resolution. For sub-100 nm devices, the use of focused ion beam becomes inevitable for exposing the region of interest on a sample cross section. The use of FIB, results concurrently in the implantation of Ga ions into the sample, which in turn, modifies its chemical composition, crystallinity and electrical properties. These structural and compositional changes are generally characterized using TEM and the studies in the past have shown that in case of silicon a 20–30 nm thick amorphous layer is formed after irradiation with 30 keV Ga ions[2,3,4,5,6]. To study the electrical impact of FIB, we employ-so-called scalpel S SRM16, a powerful method for controlled material removal that allows one to probe the third dimension
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